There is known such a semiconductor circuit that forms a spiral pattern electrode on a semiconductor substrate with using thin film forming technique and uses this pattern electrode as an inductor element. If current flows in such an inductor element that is formed on such a semiconductor substrate, magnetic flux is generated in the direction perpendicular to the spiral pattern electrode. Nevertheless, since eddy currents are induced on the front side of the semiconductor substrate by this magnetic flux to cancel effective magnetic flux, there is a problem of not effectively functioning as the inductor element. In particular, the higher a frequency of a signal that flows in the inductor element becomes, the more remarkable this inclination becomes, and hence it is difficult to form a high-frequency circuit, containing an inductor element, on a semiconductor substrate.
As conventional technology for avoiding such inconvenience, an inductor element disclosed in Japanese Patent Laid-Open No. 10-208940 is known. This inductor element has two-layer structure that a floating conductor having the same shape as an inductor conductor is sandwiched between the inductor conductor and a substrate. Hence it is possible to reduce eddy currents generated on a surface of the substrate.
By the way, in the inductor element disclosed in the Japanese Patent Laid-Open No. 10-208940, the inductor conductor and the floating conductor are being superficially formed on the substrate. Hence there is a possibility of interrupting the flow of effective magnetic flux generated by the inductor conductor depending on the configuration of lead wires extended from the inductor conductor. Therefore, there is an issue that sufficient characteristics cannot be obtained. In addition, since the floating conductor is in the state where it floats thoroughly electrically, in this floating conductor, unnecessary reflection may arise depending on a frequency and the like of a signal outputted from or inputted to the inductor conductor. Hence there is a possibility that sufficient characteristics are not obtained depending on circumstances.